1. Field of the Invention
The present invention relates to wireline operations which are typically performed within the production tubing within a well casing of a subsurface oil or gas well. More specifically, the invention is directed to a more efficient and dependable method and apparatus for retrieving long lengths of wireline, or running string, from the well when a well tool, which is attached to the remote end of the wireline, becomes lodged within the well and must be fished therefrom.
2. Description of Background and Relevant Information
Wireline operations in connection with oil and gas wells can require the use of great lengths of running string, or wireline, to the end of which can be attached any of a number of tools for performing any of a number of operations. Such operations are typically performed within the production tubing within the well casing. On occasion during the wireline operation, the tool can become lodged downhole such that the tool and the wireline connected thereto cannot be further moved within the tubing.
Prior to the present invention, the wireline operator merely had one release tool for removing the wireline, namely, the rope socket. The rope socket is simply a weak link in the wireline in the vicinity of the tool. If the tool becomes stuck downhole, tension in the wireline will either result in the dislodging of the tool or the parting of the wireline at the rope socket, so that when the lodged tool is attempted to be "fished" from the tubing, the "fishing" operation is not complicated by thousands of feet of wireline which might be coiled above the tool
In many cases, however, when wireline equipment becomes stuck downhole, and the operator elects to "pull-out" of the rope socket, the wireline parts at a location other than at the rope socket. Due to this likelihood, or at least the great possibility that the wireline will part at some location other than at the rope socket, the wireline operator frequently elects, instead, to disconnect the wireline at the surface and to unthread the wireline from the tubing as the tubing is pulled out.
This necessarily results in increasing the time required for wireline operations and it delays subsequent well operations, thereby reducing efficiency.
The prior art includes various tools which are designed for remote release from a wireline or other particular devices which suspend such tools, such as, for example, a well casing section or a casing hanger or other downhole tools. Typically, however, these release tools are complicated assemblies of parts which are specifically designed for certain operations and are not intended merely for the selective disconnection of the wireline from the remote device or tool attached thereto.
For example, U.S. Pat. No. 4,003,434 to GARRETT et al. discloses a release tool for use with well tools such as packoffs and casing heads.
A split ring (or spring-biased locking pistons) engages under a lip on the well tool to be positioned downhole. Fluid pressure in the casing acts on the upper surface of a piston to cam the split ring (or locking pistons) inwardly to disengage the release tool and permit its removal.
U.S. Pat. No. 4,273,372 to SHESHTAWY discloses a tool for lowering casing strings into the sea to a position near the ocean floor. Dogs which engage the internal surface of the casing are cammed inwardly and outwardly by a conical piston that is interconnected to said dogs by dovetail slots. The dogs are pre-loaded to the engagement position by spring pressure. Fluid pressure is applied from the surface through the handling string engaging the lower operative face of the conical piston, moving it upwardly to cam the dogs inwardly for disengagement.
U.S. Pat. No. 4,576,230 to TAPP et al. discloses an apparatus to temporarily set tools in a portion of a well casing. Toothed engaging elements are cammed outwardly from the body of the apparatus to frictionally engage the inner surface of the casing.
U.S. Pat. No. 4,603,743 to LINDSEY discloses an apparatus for setting a liner hanger in a well casing. Toothed engaging elements are hydraulically cammed outwardly to frictionally engage the inner surface of the casing.
Consequently, prior to the present invention there was a need for a releasable coupling device for use during wireline operation for universal use with various well tools, whose sole function is to permit the wireline to be selectively disconnected.